1. (a.) Not to be taken by assault; incapable of being subdued; unconquerable; as, an impregnable fortress\; impregnable virtue.

2. (a.) Capable of being impregnated, as the egg of an animal, or the ovule of a plant.

deathless defended guarded immortal impenetrable imperishable incontestable incorruptible indelible indestructible indomitable ineffaceable ineradicable inexpugnable inextinguishable insuperable invincible inviolable invulnerable irresistible mighty nonperishable overpowering overwhelming protected quenchless resistless safe safeguarded secure shielded unassailable unbeatable unconquerable undampable undefeatable undestroyable undying unquenchable unsubduable unsurmountable unyielding